The present invention relates generally to osteotomes, and more particularly to an ultrasonically driven osteotome including a tool tip having a curvature substantially corresponding to the medial curve of a hip implant.
The use of various prosthetic implant systems, such as those used for the total replacement of hips, has become increasingly more commonplace. For example, hip replacements are performed to alleviate conditions caused by osteoarthritis, rheumatoid arthritis, fractures, dislocations, congenital deformities, and other hip-related conditions.
Total hip arthroplasty involves replacing the damaged surfaces of the hip with artificial surfaces. Typically, the surgeon removes the head and neck of the femur 10 and replaces them with a femoral component 12 comprised of a metallic ball 14 and stem 16, as shown in FIG. 1. The femoral component 12 typically has a medial curve portion 18. The stem 16 is usually secured in place with the use of bone cement 20.
Occasionally, various conditions arise with the hip implant, such as the femoral component, and it becomes necessary to perform a revision procedure. As part of the revision procedure, it is sometimes necessary to remove the existing femoral component and replace it with a different femoral component.
The goal in these revision procedures is to remove the existing femoral component and surrounding cement material and preserve the integrity of the normal host tissue. An osteotome is a device which aids the orthopedic surgeon in achieving this goal. Recently, the adaptation of ultrasound technology to develop ultrasonically driven osteotomes that remove cement has made the removal of existing femoral components significantly easier.
The conventional ultrasonically driven osteotome system generally consists of a console to generate ultrasound power, an ultrasonic handpiece, and a variety of tool tips and extenders that are typically controlled by a foot switch during surgery. With the use of a piezoelectric transducer, the console converts electrical energy into mechanical energy. The mechanical energy passes through the tool tip as high frequency energy acoustic waves (20,000 to 100,000 cycles/second or hertz). The energy from the acoustic waves is transferred from the tool tip to the cement, causing intermolecular friction that converts the hard cement into a putty. Minimal heat is generated during this process.
The conventional ultrasonically driven osteotome typically comes with a variety of tool tips to aid in the different aspects of cement removal. Removal of cement is performed using both tactile and audible feedback to ensure host-bone integrity. The ultrasonically driven osteotome is capable of cutting through or perforating host bone, especially in areas of impaired integrity where the bone is thin. An audible high-pitched change in sound, or difficulty in passing the tip through an area, are both indicators that the tool tip is in contact with host bone and should be avoided. The tool tips of the ultrasonic osteotomes are typically manufactured from titanium alloys.
Although most conventional ultrasonically driven osteotomes are suitable for use on the lateral side of the proximal femur, there is significant difficulty accessing the medial side of the proximal femur (i.e., in proximity to the medial curve of the femoral component) due to the configuration of conventional tool tips, which tend to be flat and straight chisel-like members. These conventional tool tips make it especially difficult to remove cement from the area in proximity to the medial curve of the femoral component.
Therefore, there exists a need for a tool tip for an ultrasonically driven osteotome, wherein the tool tip is capable of accessing the area in proximity to the medial curve of a femoral component in order to facilitate cement removal therefrom.
In accordance with a first embodiment of the present invention, a tool tip for use as an ultrasonically driven osteotome is provided, having a member with a medial surface. The medial surface has a first radius of curvature defined by a first medial surface center point which is medial to the member and a second radius of curvature having a center point defined by a first line lateral to the member. The member further has a lateral surface with a third radius of curvature defined by a third lateral surface center point, medial to said member, and a fourth radius of curvature having a center point defined by a line lateral to said second member. The first and third radius of curvature substantially corresponds to a curve on the surface of an implant component.
In accordance with a second embodiment of the present invention, a tool tip for use as an ultrasonically driven osteotome is provided, comprising: (1) a connection portion for connecting to the osteotome; and (2) an engagement portion having a medial surface with a first radius of curvature defined by a first medial surface center point, which is medial to the member and a second radius of curvature having a center point defined by a first curved line lateral to the member. The member is further defined by a lateral surface with a third radius of curvature formed by a third lateral surface center point medial to the member, and a fourth radius of curvature having a center point defined by a curved line lateral to said second member. The fourth radius of curvature substantially corresponds to a curve on the surface of an implant component.
In accordance with a third embodiment of the present invention, an ultrasonically driven osteotome system is provided, comprising: (1) a driver member; and (2) a tool tip member, comprising: (a) a connection portion for connecting the tool tip member to the driver member; and (b) an engagement portion having a medial surface. With a first radius of curvature defined by a first medial surface center point, which is medial to the member, and a second radius of curvature having a center point defined by a first curved line, lateral to the member. The member further has a lateral surface with a third radius of curvature defined by a third lateral surface center point medial to said member and a fourth radius of curvature having a center point defined by a curved line lateral to said second member. The radius of curvature of the first, third, and fourth radius of curvature substantially corresponds to a curve on the surface of an implant component.
In accordance with a fourth embodiment of the present invention, a method of softening cement adjacent to a femoral component is provided, comprising: (1) providing an ultrasonically driven osteotome system, comprising: (a) a driver member; and (b) a tool tip member, comprising: (i) a connection portion for connecting the tool tip member to the osteotome member; and (ii) an engagement portion having a medial surface with a first radius of curvature defined by a first medial surface center point which is medial to the member and a second radius of curvature having a center point defined by a first line lateral to the member. The member further has a lateral surface with a third radius of curvature defined by a third lateral surface center point medial to the member and a fourth radius of curvature having a center point defined by a line lateral to the member. The third curvature substantially corresponds to a curve on the surface of an implant component; (2) actuating the ultrasonically driven osteotome system so as cause an energy source to be transmitted to the tool tip; and (3) contacting the cement with the tool tip, whereby the energy source causes the cement to soften.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.